(No, we’re not talking about shipping.)
Scenario A: It’s 3:00 a.m. You’re in the middle of an all-night programming session, and your console seems to be freaking out every few minutes. You, in turn, are freaking out too.
Scenario B: It’s ten in the morning. You’re thirty minutes into a corporate event, and you suddenly lose control of your rig. Someone eventually notices that the DMX optical isolator at dimmer beach is dead. You feel like you might lose control of your bowels.
Scenario C: It’s 8:00 p.m. The headline act of your outdoor festival has just launched into its first song. The lighting system seems to dim momentarily, and then your board suddenly reboots. You feel like your heart has rebooted as well.
Any one of these problems probably could have been prevented with a piece of equipment called a UPS (or Uninterruptible Power Supply). The primary intent of a UPS is to provide constant — or uninterrupted — power to an electrically powered device. It’s basically a battery pack for your sensitive electronics.
At its simplest, a UPS is a big battery. You plug your equipment into the battery, and you plug the battery into the wall. If there is a loss of power at the outlet, the battery stops charging, but you still have the battery to power your equipment until it becomes drained. Just like a flashlight, the bigger the battery, the longer you can run your equipment. Of course — as is so often the case — a UPS isn’t quite so simple, and there is a lot more important information to know.
While there are several different types of UPS units available today, the two largest categories are the online and off-line varieties. Although each type may have its own benefits, this is definitely a product where you “get what you pay for.”
In standard operation, an off-line (or standby) UPS supplies power directly to your electronics while, at the same time, charging its battery. While your equipment gets power directly from the wall, an AC-to-DC converter charges the battery. When a power failure is detected, the unit quickly switches to battery power, providing power via a DC-to-AC inverter. This switch to battery power typically happens in 4 to 25 milliseconds.
An off-line UPS provides protection from short-term power outages and low-voltage scenarios such as brownouts or, in the extreme case, a com-plete blackout. They also offer about the same high-voltage protection as the surge suppressors in everyday power strips, which is most likely a metal-oxide varistor that acts as a shunt should any high voltage, such as a lightning strike, happen to find its way to the power circuit.
An on-line UPS is significantly different in that it constantly powers the load from its internal battery. Sometimes referred to as dual conversion online systems, this type of unit is generally more costly than an off-line model of similar size, but offers major advantages over the prior. Most obvious is that no switch has to be made when a voltage drop or power outage is detected. Since your equipment is already being fed from a com-bination of batteries and capacitors, your protected equipment never knows the difference if wall power is lost.
The dual-conversion process simply indicates that the power from the wall is being converted from AC to DC and back again before it ever reaches your precious electronics. This adds significant protection from power problems like voltage spikes and irregular frequency changes.
While all this information is a great step toward understanding which UPS to buy for your needs, there are a few extra pieces to the puzzle. Most electrical equipment in the United States is designed to be run off a power grid that supplies 110 to120 volts of alternating current. The polarity of the voltage alternates 120 times per second in a 60 Hz system in the form of a nice, smooth sine wave.
Unfortunately, many DC-to-AC power inverters only switch polarity between positive and negative and actually output a square wave instead of a sine wave. While a lot of electrical equipment will still run off this type of output, it is possible that it could cause damage to some electronic equipment if it’s operated from a square wave output for extended periods. Be sure to look for a UPS that has a true sine wave output. Your equip-ment will thank you.
UPS systems should never be difficult to justify. In an industry where a typical lighting control area often can have more than $100,000 worth of equipment plugged in, spending less than 1% of that on protecting your investment seems like an easy decision. That said, a UPS has to be treated like any other piece of equipment in your shop or office. Batteries don’t last forever, and regular maintenance and testing of your UPS systems must be a priority.
Phil Gilbert is a freelance lighting designer and programmer. You can contact him at pgilbert@ plsn.com.
